1. Field of the Invention
This invention relates to an ultrasonic diagnostic apparatus, and in particular to an apparatus which displays the movement of cardiac muscle in the heart as a graph.
2. Description of the Related Art
The Applicant, in JPA-09-253085 published by the Japanese Patent Office on Sep. 30, 1997, proposes an apparatus for graphically displaying muscle movement in the human heart using transmitted/received ultrasonic waves. This device displays a two-dimensional sectional image of the left ventricle of the heart. A reference point is set in the middle of the left ventricle manually or automatically, and plural reference lines are automatically set extending radially from the reference point. The surface of the cardiac muscle (specifically endocardium) is detected by performing a technique such as edge detection, etc., on the reference lines, and cardiac muscle movement on the reference lines is displayed as a graph.
The horizontal axis in the graph shows the azimuth (address of the reference line) seen from the reference point. The vertical axis in the graph shows the amount of movement of the cardiac muscle (distance from the reference point). The graph is updated in real time. If this graph which varies with time is observed continuously, it is easy to identify which azimuth surrounding the left ventricle, i.e. which cardiac muscle part, has a disease. Specifically, the movement of cardiac muscle parts which have a disease such as for example cardiac infarction is different from the movement of other, healthy parts. In general, the amount of the movement of the diseased part is small or abnormal.
However, in the aforesaid graphical display, the part in which there is an obstruction to motion cannot easily be determined merely by observing a graph at one point in time. That is, it is only by observing the graph continuously that it is possible to identify a diseased part.
It is therefore desirable to improve the graphical display to make diagnosis of cardiac disease easier. For example, it is preferable to evaluate each part of the cardiac muscle by observing only one graph.